Spatial and temporal relationships between protected areas and threatened and endangered species

Alexandra Peers1 & Maria J. Santos 1

1. Spatial History Project, Center for Spatial and Textual Analysis; and the Bill Lane Center for the American West; Stanford University

As multiple stressors affect biodiversity persistence, conservation land acquisition has become a key tactic in preventing habitat loss, fragmentation, and land degradation, and thus maintaining biodiversity. Here we ask the question of whether land acquisition prompted the detection of threatened and endangered (T&E) species or the detection of T&E species promoted land acquisition. We used available data on plant, bird and mammal surveys throughout time, and acquired information on open space land acquisition dates in the state of California. Of the over 20,000 detections of T&E plants, birds, and mammals over the last century in California, 30-40% of all taxa were detected in land that was acquired for conservation (33% for birds, 45% for mammals, and 43% for plants). However, we were only able to obtain information on the date of acquisition for about 20% of California’s open space land (n=12,000 out of the about 54,000 properties; and about 60% of the land area). For this subset, and for the 1-5% of data where we could match date of detection and land acquisition, we found that plants were often detected after land acquisition occurred and that detection of birds and mammals occurred before land acquisition. The link between the detection of threatened and endangered species and land acquisition match the history of conservation in California. The first large extents of conservation lands in the state were acquired to protect forests and for their aesthetic value. Subsequent land acquisitions were driven by other reasons such as water management, land availability, economics of land market, open space and recreation, and later for biodiversity. The interest in biodiversity started with an interest in specific species such as game and furbearers. This led the state and research institutions to conduct surveys early in the century to determine California’s biological diversity. However, is not until 1960s that the official legislation for the conservation of threatened and endangered species is implemented at a national and state level through the Endangered Species Act (ESA). This legal instrument first focused on the protection of threatened and endangered vertebrates, and then its 1973 amendment mandated the conservation of their critical habitat. It is not until 1976 that plants and invertebrates become listed under the ESA and that protection is granted. This justifies why the detection of threatened and endangered plants occurs much later than that of vertebrates.

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Introduction

As multiple stressors affect biodiversity persistence, conservation land acquisition has become a key tactic in preventing habitat loss, fragmentation, and land degradation, and thus maintaining biodiversity. Biodiversity promotes a system’s resilience, or an ecosystem’s ability to withstand change (Holling 1973), while also facilitating ecosystem services that are beneficial for both the landscape and people (Folke et al. 2004; Nelson et al. 2009; Rands et al. 2010). Although the importance of conserving flora and fauna emerged early on in conservation history (Barton 2000; Coates 2004), many of the first protected areas were preserved for their noted geological or aesthetic qualities. For example, Yellowstone National Park, the first federally protected space in the United States established in 1872, was created for its valuable hot springs and geysers. However, biodiversity soon became an integral part of the establishment of protected spaces.

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Historically, a dichotomy formed in the ideas surrounding land conservation throughout the United States, including California. In 1864 Henry David Thoreau called for the establishment of "national preserves" of virgin forest, "not for idle sport or food, but for inspiration and our own true re-creation", inspired by the practice of forestry in British colonies (Barton 2000). In 1876, Franklin B. Hough was appointed the first Federal forestry agent, with the task of gathering statistics about the state of the nation’s forests (Barton 2000). In 1877, through the leadership of the Secretary of the Interior Carl Schurz, the Department of the Interior took an active interest in conservation issues for the first time, advocating far-sighted conservation policies, such as the creation of forest reserves and a federal forest service. After the establishment of Yellowstone and Yosemite National Parks, several areas were acquired in the form of state and national forests (Barton 2000), leading to the first Governors’ Conference on Nature Conservation in 1908. This conference was the turning point in the acquisition and establishment of protected land throughout the twentieth century. The land conservation movement was further reinforced later in the century, as focus shifted towards the preservation of biodiversity. Congress passed the Endangered Species Preservation Act in 1966, providing limited protection to federally listed endangered native species (U. S. Fish & Wildlife Service, 2011). However, it was not until 1973 that the Act defined what endangered and threatened species were and expanded the definition to include plants and invertebrates. This redefining created a push for land conservation motivated by very different goals and targeted different taxon. This is also the time that conservation scientists made a call for a more strategic and systematic approach to land acquisition to meet biodiversity targets (Cowling et al. 2001; Pressey and Bottrill 2008).

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While conservation took place in many parts of the United States, we chose to focus on California. California is not only one of the most biodiverse areas in the United States, it is one of the most biodiverse regions on the earth: the California Floristic Province is one of the world’s 25 most diverse areas on the planet (Calsbeek et al. 2003). 44% of the earth’s plants and 35% of the earth’s terrestrial vertebrates are found only in these 25 hotspots, despite the fact these hotspots make up just 1.4% of the world’s land cover (Brooks et al. 2002). For California itself, 44% of its plant and vertebrate species are endemic to the state (Calsbeek et al. 2003). These biodiversity hotspots have immense implications for conservation strategies, as calls within the ecological community have been made to conserve land in these zones in order to protect large number of species living in relatively small regions of land.

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The overarching question of our research explored the spatial and temporal relationship between protected areas acquisition and threatened and endangered (T&E) species over the 20th century. This question had several subcomponents: first, assessing whether T&E species were detected inside or outside of protected areas; second, assessing whether protected areas were established before or after the detection of T&E species; and third, assessing whether detection of T&E mammals, birds, and plants experience match the time and location of establishment protected areas. To answer these questions we merged available data documenting the detection of T&E species in California and the extent and establishment of parks, preserves, and open spaces of the state.

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Methods

Our study area extended to the whole of California. We obtained the geospatial data for all open spaces in California from the California Protected Area Database (GreenInfo Network, 2012). We contacted managing agencies to assign acquisition and establishment dates to each protected area property. For most of the properties these two dates were similar, with the exception of lands that were purchased by different agencies throughout time, or lands that lost their conservation status.

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We used the California Department of Fish and Game lists of threatened and endangered (T&E) mammals, birds, and plants (California Department of Fish and Game, 2011; California Department of Fish and Game, 2012). These lists contain the species considered T&E by both the state and federal governments. For the T&E mammal and bird species, we used the online databases Arctos (University of Alaska Museum of the North et al., 2011) and MaNIS (Regents of the University of California, 2012) to find their historical extents. We used Arctos to obtain information for both mammals and birds, and MaNIS for mammal records. The T&E plant data came from the Consortium of California Herbaria (University of California Jepson Herbarium, 2011; Wolf et al. 2011). It is important to note that these data sets represent state and research surveys and are by no means an extensive depiction of all possible detections of T&E species. Nonetheless, we believe that the spatial and temporal depictions of these data sets can be illustrative of patterns of T&E detection in concert with those of conservation land acquisition.

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First we assessed whether there was a spatial match or mismatch between open spaces and T&E species by overlaying the spatial representation of species detections with that of open spaces and counting the number of detections inside and outside open space. We also wanted to assess whether there were differences in the number of detections inside and outside open spaces. To do this we plotted T&E detections inside open space against T&E detections outside open space. If T&E detections were spatially mismatched with open space, so that more species were found outside than inside open spaces, this might suggest that protected areas were not well targeted, if they were targeted at all, to protect T&E species.

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Second, we asked whether there was a temporal match or mismatch between open spaces and T&E species. To do this we created a subset of the species location data and open space acquisition data, and assessed how many times the decade of T&E detection matched the decade of open space acquisition. We then analyzed how much delay occurred in acquiring conservation land after T&E species were detected, and how much delay occurred in detecting T&E species after land was acquired. To do this we calculated the difference between the decade in which T&E species detection and open space establishment occurred. Positive values indicated delay to detection and negative values indicated delay to establishment.

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We also asked whether mammals, birds, and plants experienced similar patterns of spatial and temporal match or mismatch with open spaces. To answer this question we repeated the analysis outlined above for each taxa separately.

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Results

We collected over 20,000 locations of T&E plants, birds and mammals detected in California over the last century (Table 1). These comprised over 150 genus and more than 250 species. The attribution of land acquisition dates was less successful, as we were only able to collect establishment dates for 12,000 of the ca. 54,000 protected properties in California. Nonetheless, this 22% of the total properties corresponds to about 60% of the state’s land designated as protected areas, so we believe that this preliminary analysis is likely robust.

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Historical timeline of land acquisition and T&E species detection: We found very different historical timelines for T&E species detections and land acquisition (Figure 1a). We found that large tracts of land were acquired in the beginning of the 20th century, whilst detections of T&E species peaked in the 1920s for birds, 1930-40s for mammals, and 1980s for plants. Cumulatively, we found asymptotic curves for both land acquisition and T&E mammal and bird detection; T&E plant detection did not reach an asymptote, i.e. there were likely more T&E plants to be detected than those reported (Figure 1b). Looking into inside open space alone, we found similar patterns both for the peak detections of T&E species (Figure 1c) and the cumulative detections (Figure 1d).

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Figure 1a. Timeline of Open Space Acquisition and Species Detection: Total

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Figure 1b. Timeline of Open Space Acquisition and Species Detection: Cumulative Totals

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Figure 1c. Timeline of Open Space Acquisition and Species Detection: Inside Open Space

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Figure 1d. Timeline of Open Space Acquisition and Species Detection: Cumulative Inside Open Space

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Spatial match or mismatch between open spaces and T&E species: Between 30-40% of T&E species were detected in what are today open space areas. We found 33% of T&E birds, 45% of T&E mammals, and 43% T&E plants detections inside current open space areas (n=1622, n=5249, and n=2249, respectively). We found a higher number of detections outside open space than inside open space for all taxa, although exceptions occurred for all taxa during some periods, in the 2000s for plants (Figure 2a), 1980s to today for birds (Figure 2b), and 1920s and 1970s for mammals (Figure 2c).

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Figure 2a. Timeline Of T&E Detections In Areas Today Defined As Open Space And Not Open Space: Plants

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Figure 2b. Timeline Of T&E Detections In Areas Today Defined As Open Space And Not Open Space: Birds

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Figure 2c. Timeline Of T&E Detections In Areas Today Defined As Open Space And Not Open Space: Mammals

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Temporal match or mismatch between open spaces and T&E species: For the T&E detections that we could match with the acquisition dates of the open spaces, we found that a reduced number of detections occurred in the same decade of land acquisition (Birds: n=3; Mammals: n=8; Plants: n=9; Figure 3a). On average, it took twice as many years to acquire lands after the detection of a T&E species than it took to detect a T&E species after land was acquired (land acquisition: meanąst.dev.=19.6ą19.25years; T&E species: meanąst.dev. = 10.3ą21.22years). Further, the detection of T&E birds and mammals occurred before land acquisition, while plants’ detection occurred mostly after land acquisition (Figure 3b).

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Figure 3a. Temporal matching between the detection of T&E species and land acquisition:matching the detection of T&E and land acquisition

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Figure 3b. Temporal matching between the detection of T&E species and land acquisition: average delay in the detection of T&E species and establishment.

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We developed an interactive visualization to simultaneously depict the dynamics of the detections of T&E species and land acquisition (Figure 4). In this interactive graph we display the individual taxa and open space acquisitions along a timeline, using the forward and backward arrows on the upper right to navigate the timeline. At each time-point we display the numbers corresponding to the prior decade. For example, in 1920 the map displays all T&E species detected and open space acquired until 1920. Dynamically, the histogram shows the number of detections of each taxa that were found inside (lower area of the histogram) and outside (upper area of the histogram) for the previous decade, so that for the 1920s example, the histogram will display 1910-1919 data. The right most bar chart shows the area of open space in comparison to California land area. The bar chart shows the historic extent of open space, as well as the open space established in the past decade. Returning to the example for 1920, the bar chart shows all of the open space established up to 1920, as well as the open space specifically established in 1910-1919 (bottom of the bar). In the background of California we display the 2012 open space area.

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Figure 4. Interactive Visualization

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Large Format Viewer

Discussion

Biodiversity protection through conservation land acquisition has been the most common strategy applied in California, the United States, and likely the world. Historically, land acquisition has occurred somewhat opportunistically (Pressey and Bottrill 2008). In 1970s there was a shift towards systematic assessments for the selection of the best areas to acquire to protect multiple conservation goals (Cowling et al. 2001) and these systematic approaches remain in place today (Pressey and Bottrill 2008). Subsequently Meir et al. (2004) have argued that negative ramifications could result from delaying conservation acquisition decisions over time, as higher priority areas may not be available for acquisition when funding is available and vice versa. There could also be opportunity costs associated with delaying land conservation acquisition at the expense of improving knowledge (Grantham et al. 2009). Comparing and contrasting the timelines of land acquisition and T&E species detection over the last century could provide empirical evidence of these reported trade-offs.

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Our results show that the peak of land acquisition in California occurred in the beginning at the turn of the century. This corresponds to the acquisition of large tracts of federal land placed under the ownership and management of the National Park Service or Forest Service. The 1930s peak of land acquisition corresponds to California State Parks acquisitions and the 1980s to federal land acquisition. These peaks of land acquisition, however, do not match the peaks of T&E species detections and the spatial locations at which these occurred. Mammal and bird T&E species detections peaked from 1910 to 1940, which corresponds to the surveys lead by Joseph Grinnell, director of the Museum of Vertebrate Zoology, University of California Berkeley, from 1907 to 1939 (Museum of Vertebrate Zoology, 2012). For plants, the detection peaks occurred in the 1930s and again in the 1980s. The 1930s peak of detections corresponds to the survey lead by Albert Wieslander for the United States Forest Services. The surveys aimed at the first assessment of the state’s forest resources (Wieslander 1935). Many of these species were, in fact, listed as T&E after these surveys, and some as a result of these surveys.

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Biodiversity hotspots are likely those that hold viable populations of T&E species (Brooks et al. 2004). A great amount of California’s biodiversity is now found in protected areas. 30-40% of the total detections of T&E species occurred in what are today open space areas, which correspond to about 40% of the state. However, we found very little spatio-temporal matching between species detection and open space establishment. Only 3-8% of detections of T&E occurred at the same spatial location and within the same decade as the land was acquired for conservation. This suggests that fauna and flora surveys in the state of California were temporally detached from conservation land acquisition. Surveys and land acquisition were driven by different missions, strategies, ideas, and funding. The first large extents of conservation lands in the state were acquired to protect forests and for their aesthetic value. Subsequent land acquisitions were driven by other reasons such as water management, land availability, economics of the land market, open space and recreation, and later for biodiversity. Additionally there was a transition from the early 20th century top-down state level control of land use, passing through the obstruction of development in the 1970s, to the smart growth movement in the 1990s. These changes in controls on land use also dictated an additional source of funding for land acquisition, a funding source that was largely independent of the motivations and funding available for biodiversity assessments.

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Our results also demonstrate taxonomic biases in species detection and land acquisition, suggesting that land was acquired after the detection of T&E species of mammals and birds. The interest in biodiversity started with an early interest in specific game and furbearer species. This led the state, academic institutions, and museums to conduct surveys early in the century to determine California’s biological diversity. However, it was not until the 1960s that official legislation for the conservation of T&E species was implemented at a national and state level through the Endangered Species Act (ESA). This legal instrument first focused on the protection of T&E vertebrates, and only in its 1973 amendment instated the conservation of critical habitat for T&E species. It was not until 1976 that plants and invertebrates became listed under the ESA and granted protection. This is likely why the detection of T&E was delayed in relation to the acquisition of conservation land. These results suggest that more T&E species are likely to still be detected in existing open space areas, as detections did not reach an asymptote throughout the 20th century.

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Despite these divergent timelines of T&E species detection and open space acquisition, it is important to note that a large amount of the state biological diversity is now under some sort of protection. Independent of the motivation for which land was acquired, either by cultural or aesthetic values or by the detection of species, it is important to emphasize the need to maintain these protected areas in order to maintain the high biodiversity characteristic of California.

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Acknowledgements

This research is part of the program of Maria J. Santos postdoctoral fellowship funded by the Bill Lane Center for the American West and the Wallenberg Foundation through the Spatial History Project. Alexandra Peers received credit towards her undergraduate degree during the academic year and was funded by the Vice-Provost for Undergraduate Education during the summer. We are very thankful to Dr. Jon Christensen and Dr. Zephyr Frank for their mentorship and their great insight into the project. We also thank the staff at CESTA, including Jake Coolidge and Erik Steiner, for their support. This research also ties into Stanford’s City Nature project.

The Spatial History Project at Stanford University, a part of the Center for Spatial and Textual Analysis, is made possible by the generous funding of the Vice Provost for Undergraduate Education (VPUE), DoResearch, The Andrew W. Mellon Foundation, and The Wallenberg Foundation Media Places Initiative.